U.S. patent number 7,032,918 [Application Number 10/499,585] was granted by the patent office on 2006-04-25 for stabilization of an articulated vehicle.
This patent grant is currently assigned to John Deere Forestry Oy. Invention is credited to Veli-Matti Jortikka, Mikko Rahja, Into Saarinen.
United States Patent |
7,032,918 |
Saarinen , et al. |
April 25, 2006 |
Stabilization of an articulated vehicle
Abstract
A method for stabilizing an articulated vehicle, which
articulated vehicle comprises at least a front frame structure and
a rear frame structure, and a frame joint structure, which is
arranged to couple the frame structures to each other and to allow
them to rotate both in relation to each other, away from the normal
position, as well as at the same time around an axis, which is
substantially parallel to the longitudinal direction of the
articulated vehicle. In the method a supporting force is
maintained, which force affects between the frame structures and
resists the rotation of the frame structures away from normal
position, and the maximum of said supporting force is controlled in
such a manner that it is dependent on the difference of rotations
at least when said difference is increasing and at least when said
difference is static.
Inventors: |
Saarinen; Into (Pirkkala,
FI), Jortikka; Veli-Matti (Tampere, FI),
Rahja; Mikko (Ylojarvi, FI) |
Assignee: |
John Deere Forestry Oy
(Tampere, FI)
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Family
ID: |
8562552 |
Appl.
No.: |
10/499,585 |
Filed: |
December 19, 2002 |
PCT
Filed: |
December 19, 2002 |
PCT No.: |
PCT/FI02/01045 |
371(c)(1),(2),(4) Date: |
June 18, 2004 |
PCT
Pub. No.: |
WO03/055735 |
PCT
Pub. Date: |
July 10, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050092540 A1 |
May 5, 2005 |
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Foreign Application Priority Data
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Dec 21, 2001 [FI] |
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20012545 |
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Current U.S.
Class: |
280/455.1;
280/474; 280/492 |
Current CPC
Class: |
B60D
1/32 (20130101); B62D 12/00 (20130101); B62D
53/0871 (20130101) |
Current International
Class: |
B62D
53/00 (20060101) |
Field of
Search: |
;280/455.1,474,492
;180/124.111,124.112 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3615071 |
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Nov 1987 |
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DE |
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444 077 |
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Jun 1983 |
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SE |
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WO 92/11155 |
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Jul 1992 |
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WO |
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WO 95/17328 |
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Jun 1995 |
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WO |
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WO 00/35735 |
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Jun 2000 |
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WO |
|
Other References
International Preliminary Examination Report, Form PCT/IPEA/409, as
issued by the Swedish Patent Office in Connection with PCT
Application No. PCT/FI022/01045, Feb. 2004. cited by other.
|
Primary Examiner: Hurley; Kevin
Attorney, Agent or Firm: Quarles & Brady LLP
Claims
The invention claimed is:
1. A method for stabilizing an articulated vehicle, which vehicle
is forest working machine comprising at least: a front frame
construction and a rear frame construction, and a frame joint
construction, which is arranged to couple the frame structures with
each other and to allow their rotation both in relation to each
other, away from normal position, and at the same time around a
horizontal axis, which is substantially parallel to the
longitudinal direction of the articulated vehicle, wherein the
method comprises the steps of: maintaining an increasing supporting
force, which supporting force affects between the frame structures,
stabilizes the rotating frame structure by resisting the rotation
of the rotating frame structure away from said normal position
around said horizontal axis, and controlling the maximum of said
supporting force in such a manner that it depends on the difference
of rotations of the frame structures, at least when said difference
is increasing, and at least when said difference is static, wherein
the supporting force is the greater the greater the difference
is.
2. The method according to claim 1, further comprising the step of
removing said supporting force at least when said difference is
decreasing, and at least when the difference of rotation is static
and the frame structures do not tend to rotate away from normal
position.
3. The method according to claim 1, wherein the supporting force
increases progressively with the increasing difference of
rotation.
4. The method according to claim 2, wherein the supporting force
increases progressively with the increasing difference of
rotation.
5. A system for stabilizing an articulated vehicle, which vehicle
is a forest working machine comprising at least: a front frame
construction and a rear frame construction, and a frame joint
construction, which is arranged to couple the frame structures with
each other and to allow their rotation both in relation to each
other, away from normal position, and at the same time around a
horizontal axis, which is substantially parallel to the
longitudinal direction of the articulated vehicle, actuator and
control means, which are arranged to transfer an increasing
supporting force, which affects between the frame structures,
stabilizes the rotating frame structure by resisting the rotation
of the rotating frame structure away from said normal position
around said horizontal axis, and to control the maximum of said
supporting force in such a manner that it depends on the difference
of rotations of the frame structures, at least when said difference
is increasing, and at least when said difference is static, wherein
the supporting force is the greater the greater the difference
is.
6. The system according to claim 5, wherein the actuator and
control means are in addition arranged to couple said supporting
force off at least when said difference is decreasing, and at least
when the difference of rotation is static and the frame structures
do not tend to rotate away from normal position.
7. The system according to claim 5, wherein the supporting force is
substantially constant or zero in normal position and around
it.
8. The system according to claim 5, wherein the supporting force is
arranged to increase progressively with the increasing difference
of rotation.
9. The system according to claim 5, wherein the actuator and
control means are in addition arranged to lock the frame structures
at the desired mutual positions, in which case the difference of
rotation cannot change either.
10. The system according to claim 5, wherein the actuator and
control means comprise: at least one cylinder, which is operated by
a pressurized medium and arranged to change its length when the
frame structures rotate, and at least one controlled pressure
valve, which is arranged to limit the maximum pressure of the
pressurized medium leaving the cylinder, and at the same time the
supporting force in such a manner that the maximum pressure depends
on the difference of rotations.
11. The system according to claim 5, wherein the actuator and
control means comprise in addition pressurized-medium-operated,
electric and/or mechanic means, which are arranged to indicate the
difference of rotations.
12. The system according to claim 5, wherein the actuator and
control means further comprise: a profile form, which moves with
the first frame structure, and a follower device which moves with
the second frame structure, in which case said follower device at
the same time moves along said profile form in such a manner that
the mutual position of the profile form and the follower device is
at the same time dependent on the difference of rotations.
13. The system according to claim 11, wherein the
pressurized-medium-operated, electric and/or mechanic means are
arranged directly to control at least one pressure valve, which is
arranged to limit the maximum pressure of the pressurized medium
used in the system, and at the same time the supporting force in
such a manner that the maximum pressure depends on the difference
of rotations.
14. The system according to claim 5, wherein the frame joint
structure comprises: a first rim mounted on a bearing, which
rotates with the first frame structure, and a second rim mounted on
a bearing, which rotates with the second frame structure, and
wherein the actuator and control means comprise at least one
cylinder, which is operated by a pressurized medium and arranged to
change its length when the frame structures rotate, in which case
it is coupled either between the first rim and the second frame
structure or the second rim and the first frame structure.
15. The system according to claim 5, wherein the actuator and
control means comprise a control system of the articulated vehicle,
as whose input is one or more control signals, on the basis of
which the difference of rotations can be determined, and as whose
output is a second control signal, which corresponds to the desired
supporting control system, which algorithm is modifiable and on the
basis of which the second control signal can be determined on the
basis of said one or more control signals.
16. The system according to claim 5, wherein the articulated
vehicle is a first working machine meant to move on terrain,
especially a forwarder, in which case the front frame is equipped
with a control cabin, the rear frame is equipped with a load space,
and one of the frames is, in addition, equipped with at least one
turning boom assembly.
17. The system according to claim 5, wherein as a normal position
is a position, wherein the frame constructions are when the
articulated vehicle is placed on a flat surface.
18. The system according to claim 6, wherein the supporting force
is substantially constant or zero in normal position and around
it.
19. The system according to claim 6, wherein the actuator and
control means comprise: at least one cylinder, which is operated by
a pressurized medium and arranged to change its length when the
frame structures rotate, and at least one controlled pressure
valve, which is arranged to limit the maximum pressure of the
pressurized medium leaving the cylinder, and at the same time the
supporting force in such a manner that the maximum pressure depends
on the difference of rotations.
20. The system according to claim 9, wherein the actuator and
control means comprise: at least one cylinder, which is operated by
a pressurized medium and arranged to change its length when the
frame structures rotate, and at least one controlled pressure
valve, which is arranged to limit the maximum pressure of the
pressurized medium leaving the cylinder, and at the same time the
supporting force in such a manner that the maximum pressure depends
on the difference of rotations.
21. The system according to claim 10, wherein the actuator and
control means comprise in addition pressurized-medium-operated,
electric and/or mechanic means, which are arranged to indicate the
difference of rotations.
22. The system according to claim 10, wherein the actuator and
control means further comprise: a profile form, which moves with
the first frame structure, and a follower device which moves with
the second frame structure, in which case said follower device at
the same time moves along said profile form in such a manner that
the mutual position of the profile form and the follower device is
at the same time dependent on the difference of rotations.
23. The system according to claim 12, wherein the
pressurized-medium-operated, electric and/or mechanic means are
arranged directly to control at least one pressure valve, which is
arranged to limit the maximum pressure of the pressurized medium
used in the system, and at the same time the supporting force in
such a manner that the maximum pressure depends on the difference
of rotations.
24. The system according to claim 10, wherein the actuator and
control means comprise a control system of the articulated vehicle,
as whose input is one or more control signals, on the basis of
which the difference of rotations can be determined, and as whose
output is a second control signal, which corresponds to the desired
supporting control force, in which case a calculation or change
algorithm is saved in the control system, which algorithm is
modifiable and on the basis of which the second control signal can
be determined on the basis of said one or more control signals.
25. The system according to claim 24, wherein the actuator and
control means comprise in addition pressurized-medium-operated,
electric and/or mechanic means, which are arranged to indicate the
difference of rotations, for example, as pressure, electronic
signal, shift and/or position.
26. The system according to claim 16, wherein the front frame is
equipped with a power source.
27. The system according to claim 11, wherein said
pressurized-medium-operated, electric and/or mechanic means are
arranged to indicate the difference of rotations as pressure,
electronic signal, shift and/or position.
28. The system according to claim 21, wherein said
pressurized-medium-operated, electric and/or mechanic means are
arranged to indicate the difference of rotations as pressure,
electronic signal, shift and/or position.
29. The system according to claim 25, wherein said
pressurized-medium-operated, electric and/or mechanic means are
arranged to indicate the difference of rotations as pressure,
electronic signal, shift and/or position.
Description
FIELD OF THE INVENTION
The invention relates to a method for stabilizing an articulated
vehicle. The invention also relates to a system for stabilizing an
articulated vehicle.
BACKGROUND OF THE INVENTION
There are known articulated vehicles, such as harvesters, which
move on a terrain and perform harvesting, and which are equipped
with a so-called harvester head at the end of a boom assembly for
cutting and felling a growing tree stem and for sawing the stem to
pieces of desired length. The sawed tree stems are collected with
another known working machine that moves on a terrain, wherein the
working machine in question is a forwarder equipped with a grapple
and the stems are transported in its load space. There are also
known combined machines in which the functions of a harvester and a
forwarder have been combined, wherein the loading grapple can be
replaced with a harvester head that is also suitable for loading or
there are several boom assemblies in the machine.
Typically combined machines and forwarders comprise two successive
frame structures, which are arranged to turn around a vertical axis
and/or rotate around a horizontal axis in relation to each other by
means of a frame joint. In forwarders the front frame is supported,
for example, by one pair of wheels, and a cabin and a power source
are placed thereon. A load space and a boom assembly are placed on
top of the rear frame, said boom assembly being located between the
cabin and the load space. The rear frame is supported, for example,
by two pairs of wheels. The wheels can also be replaced by a bogie,
which typically comprises two wheels that sway together.
If the joint allows the frames to rotate, the function in question
is typically prevented during the operation when the vehicle is
stopped. Thus the frame joint is locked. Such a heavy rear frame
and its load are supported and receive supporting force and a
support moment from the front frame as well. The supporting forces
are finally affected by a wheel, which presses against the ground,
or by a mass of another frame alone. Supporting forces are
necessary, because the boom assembly is used to handle even heavy
tree stems, which may be very far on the side of the vehicle. When
the vehicle is mobile, the frame joint is released, and therefore
the rear frame cannot lean on the front frame and vice versa. When
moving on a terrain, the soil is considerably uneven and the
vehicle must be sufficiently stable, because otherwise the
unevenness of the terrain can, for example, cause the load space to
sway or, in an extreme case, to fall. One critical moment is the
start-off at a situation, wherein the center of gravity of the boom
assembly and/or the load space has settled in an unfavourable
manner and the rear frame leans on the front frame via the frame
joint. When the frame joint opens, the supporting forces exit and
the load space can fall or sway even fiercely, in which case the
sway itself can cause the vehicle to finally fall. The fall is
caused, for example, by the weight completely shifting on to the
wheels supporting the load space, in which situation the terrain
may yield.
A rotating frame joint is introduced in U.S. Pat. No. 4,079,955,
wherein the locking is based on the use of a disc brake. U.S. Pat.
No. 5,328,197 introduces a forwarder, wherein the frame joint
allows rotation around the longitudinal direction and folding
around the transverse direction. Rotation is locked by closing the
position of cylinders by means of valves. U.S. Pat. No. 4,444,409
also introduces a frame joint of a working machine, wherein free
movement is limited by means of mechanical limits. U.S. Pat. No.
4,535,572 introduces a tractor joint, in connection with which are
two cylinders by means of which the rotation can be affected, in
which case the volume flow coming to or leaving the cylinder is
choked. PCT-application WO 00/35735 introduces a frame joint of a
special vehicle, which connects two frames and which can be
disconnected from one frame. The frame joint includes a cylinder,
which takes care of the connection and at the same time functions
as a shock absorber.
The shock absorption described above, which is typically based on
the choking of air or fluid, affects the stability of a working
machine, but prevents the occurrence of violent and fast sways
only. The speed of a medium travelling via choking increases if the
pressure difference over the choker increases. This means that even
in the same rotation position of the frames the intensity of
absorption depends purely on the rotation speed and dynamics of the
frames, in which case there is necessarily no absorption at all
with very slow movement.
During absorption the load and balance situation of the working
machine can change, in which case the return to a stable state may
be easier. However, if the situation has not changed, the working
machine or one of its frame parts falls no matter what, but slower.
The shock absorption is based purely on the speed of the absorbed
movement, i.e. the rotation speed of the frame parts, but it does
not prevent the movement from continuing as slow and, for example,
the load space from falling. In this situation the frame joint
could naturally be locked, if there is time, but the sway of masses
caused by the stopping would cause the load space to finally fall.
Thus, according to background art, the frame joints and their shock
absorptions do not function in the best possible manner in order to
a stabilize the working machine even in states of change. A
continuously effective absorption may limit and slow down the
normal rotation of the frame parts too much, which then can cause
many load variations between different wheels and driving on
terrain is disturbed.
SUMMARY OF THE INVENTION
It is an aim of the present invention to remove the aforementioned
problems and carry out a system, which generates, between the
different frame parts of the working machine, the desired varying
supporting force or supporting moment, which is effective even in a
completely static situation.
The system functions especially in a situation, wherein the frames
rotate heavily away from normal position, but it allows them to
return to normal position freely. The supporting force offered by
the system also changes the more the further away from normal
position the frames move, in which case the normal run of the
working machine is not affected with an unnecessarily strong
effect, even if the rotation speed is high. With tilting of the
working machine the required supporting forces increase, and
therefore it is possible with the system to ensure adequate
stability for these situations and at the same time to slow down
the fast movement. The frame part can rotate and it is allowed to
stop, but even then the supporting forces are sustained statically,
which differs from normal dynamic absorption. This also means that
when starting a drive and when the frame joint is released, the
frames have a supporting force in this situation also, if
necessary. With the system the working machine is more stable in
situations of change, and therefore it is easier to control. In
connection with a sway, the movement of the frame is not stopped
suddenly, thereby decreasing the danger of falling. Progressive
function is especially useful from the point of view of the system.
With the presented control circuit it is possible to implement very
different controls, which depend on the rotation position.
The invention is suitable for use especially in forwarders, which
comprise two connected frames, in which case the cabin and power
source are placed in the front frame and the load space for tree
stems is in the rear frame. One of more boom assemblies are
attached on top of the front or rear frame. The number of wheels
supporting the frames varies and instead of them, also a
caterpillar track can be used. The invention is preferably applied
with cylinder actuators, which are simultaneously used for locking
the frame joints.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention will be described in more detail by
a preferred embodiment, wherein reference is at the same time made
to the appended drawings, in which
FIG. 1 shows actuator and control means of the system and their
arrangements according to the first embodiment of the
invention,
FIG. 2 shows actuator and control means of the system and their
arrangements according to the second embodiment of the
invention,
FIG. 3 shows the operating principle of the invention as a
graph.
DETAILED DESCRIPTION OF THE INVENTION
The control circuit according to the first embodiment which is
applied in the invention is in accordance with FIG. 1. The figure
shows a frame joint 1 and the machine in a way that presents the
principle of the implementation. A more detailed structure is
explained e.g. in connection with this description. Frame joint 1
of the working machine is described with the outer rim 3 and the
inner rim 2, which are fitted together with a bearing and which
describe a circumferential bearing of the frame joint 1 or a
corresponding system and the construction of frame joint 1
connected to it. The outer rim 3 rotates with frame 5 and the inner
rim 2 rotates with rear frame 4. If frame 4, which in this case is
the rear frame, and frame 5, which in this case is the front frame,
in addition rotate around the vertical direction with respect to
each other, the outer rim 3 is attached to that part of joint 1,
which is attached to front frame 5 by means of a vertical joint.
The position of the part in question in relation to front frame 5,
and at the same time the position of rims 2, 3 in relation to front
frame 5 are controlled, for example, by means of two horizontal
pressurized-medium-operated cylinder actuators. The rotation
position of rims 2, 3 in relation to rear frame 4 remains the same.
At the same time, front frame 5 rotates in relation to rear frame 4
and the direction of motion of the working machine changes. By
means of frame joint 1 frames 4, 5 rotate around the horizontal
rotation axis X, which at the same time is the longitudinal axis of
the working machine.
In the following, we will discuss actuator and control means 6 to
32 of the invention. Locking circuit 15 of the invention is used to
control two cylinders 6 and 7, which are operated by a pressurized
medium, perform linear reciprocating strokes, and share the load.
The system functions with one cylinder as well. They are attached
by means of joints, in which case their position is allowed to
change when frame joint 1 rotates. They are in a transverse
direction in relation to the rotation axis X. Cylinders 6, 7 create
the necessary moment of resistance by means of auxiliary circuit
27. Cylinders 6, 7 are attached on one hand to outer rim 3 or some
structure, which rotates with outer rim 3, and on the other hand to
rear frame 4 or some structure, which rotates with rear frame 4.
Cylinders 6, 7 are coupled in such a manner that when cylinder 6
extends, cylinder 7 shortens and vice versa, in which case they
typically are at least partly placed on different sides of frame
joint 1. In view of operation the position of each cylinder 6, 7
can also be reverse to FIG. 1. In FIG. 1 a pressurized medium input
to a first chamber extends the cylinder and correspondingly a
pressurized medium input to a second chamber shortens the
cylinder.
Each cylinder 6, 7 comprises a first displacement chamber and a
second displacement chamber. One of these chambers is a so-called
piston rod side chamber. Cylinders 6, 7 are especially so-called
frame brake cylinders, between which the medium can move freely
through an open valve. The valve is placed in one or two channels,
which lead from the inflating chamber to the deflating chamber.
Frame joint 1 can be locked so that the valve is closed, in which
case travel of the medium and movement of the cylinders is
prevented. Thus the outer rim 3 cannot rotate around inner rim 2
either. For example, a directional valve 18 and its central
position and left position function as the valve in question.
A working machine typically comprises a control system, which
comprises a pressure source or pressure line 16, where the locking
circuit 15 of the invention is connected to. A feed valve 14 is
typically also between the pressure source 16 and locking circuit
15, which valve is, for example, an adjustable, directly controlled
and spring-loaded pressure relief valve, whose function is to
maintain the set pressure on lines 8 and 9. Valve 14 is, through
check valve 12, connected to line 9, which is connected to the
first chamber of cylinder 7 and to the second chamber of cylinder
6. Valve 14 is, through check valve 13, connected to line 8, which
is connected to the first volume of cylinder 6 and to the second
volume of cylinder 7. Line 9 is connected to line 8 through
pressure relief valve 10 and line 8 is connected to line 9 through
pressure relief valve 11. Valves 11 and 12 function as so-called
shock valves, whose function is to open at a set pressure, if the
pressure on line 8 or 9 is too high, for example, from the point of
view of the equipment, the control circuit or especially the
durability of cylinders 6 or 7. Valves 11, 12 are, for example,
spring-loaded valves, which are set mechanically. They set the
highest pressure level of control circuit 15.
In the first embodiment of auxiliary control circuit 27, lines 8
and 9 can be connected also by means of a three- or two-positioned
four-way directional valve 18, which is typically electrically
controlled. Control is provided by control system 32, which is
controlled by command of the user of the working machine, which
command is, for example, pressing a button, moving a control stick,
or in a computerized system, selecting from a menu, which is
described in the display means of control system 32. A system
already existing in the working machine typically functions as a
control system 32, which is modified in such manner that the
functions of the invention and the control of the auxiliary control
circuit 27 are possible. The left position of directional valve 18
couples lines 8 and 9 together, in which case the rotation of frame
joint 1 is free; the middle position closes both lines 8 and 9, in
which case the frame joint is locked, because the movement of
cylinders 6 and 7 is prevented; and the right position couples
lines 8 and 9 to auxiliary control circuit 27, which ensures that
the pressure level of lines 8, 9 changes in relation to the
rotation position between outer rim 3 and inner rim 2. Thus we
discuss especially how much the front frame 5 and rear frame 4
rotate in relation to the known mutual reference or zero-position,
which is typically the position wherein the working machine and its
frames are on an even base, such as a road.
The basis of control is a relative difference between the rotation
of rims 2, 3 and not the absolute number of rotations in-relation
to, for example, the horizontal level. In order to determine the
relative difference, it is not necessary to use electric sensors,
but a simple, purely mechanic solution, which is coupled between
the rotating frames 4, 5, is enough. Thus it is a question of, for
example, control profiles or profile forms 25, 26, which are placed
suitably in relation to the controlled valves 21, 22. By changing
the placement, the timing and function of the entire system is
controlled in the vicinity of reference position N. The form of
profiles 25, 26 control the changes in supporting forces Fa, Fb
when the rotation increases and the profiles are more suitably
changed. Especially useful is a lever or wedge arrangement, whose
position depends on the position of frame joint 1. The adjustment,
profile and format of the wedge and lever have a direct effect on
what kind of control the valves 21, 22 receive.
The abovementioned reference position can be selected differently
as well for special situations, in which case the frame joint
comprises an electric sensor system, which is connected to control
32, on the basis of which the relative difference between rims 2, 3
can be determined. Thus, also valves 21, 22 are to be controlled
electrically with system 32, because the relation between control
and position is not standardized. Reference position N is
preferably stable, so that a simple mechanic system can be placed
in frame joint 1.
The mechanic system can be replaced partly with, for example,
electric limit switches, whose position controls the electrically
controlled valves 21 or 22 of the series or their pilot operations
to the desired positions in order to create the desired pressure
level. The limit switch can be replaced with a sensor, whose
position changes by control of stop 25, 26 and which is connected
to control system 32. A continuous control is the most suitable
type for the invention and a step-like function is implemented by
using several limit switches, which replace control 23, 24 and
which function at different moments. In frame joint 1, there is,
for example, a mechanic stop 25, 26 or a glide, which controls the
valve, pilot operation valve, limit switch and for instance the
position of the potential divider of the sensor, on the basis of
whose signal it is possible to determine the rotation difference.
The control of one or more valves 21, 22 of the auxiliary control
circuit 27 depends on the position of the potential divider. It is
possible to place, for example, a pulse sensor inside the frame
joint 1, which sensor moves with the inner rim 2, and the sensor is
rotated by a cogging attached on the outer rim 3. Other sensor
types are also known, and they are suitable to be placed in frame
joint 1 and with them it is possible to determine the relative
position of rims 2, 3. A suitable algorithm, chart, formula or the
like, which is most suitably modified in the desired manner and on
the basis of whose feed signal the output signal controlling the
valve means is concluded, is saved in the computer of control
system 32. With reference to FIG. 1, for example profile 25 can be
attached to valve 21 and the cam roll or stop is attached to the
frame. In FIG. 1 valves 21, 22 are attached to the rear frame 4 (or
inner rim 2) and profiles 25, 26 are attached to the front frame 5
(or outer rim 3). The purpose of mediums 23 to 26 is to indicate
the rotation difference as, for example, pressure, electronic
signal, shift and/or position.
Auxiliary control circuit 27 comprises line 19, which can be
combined to line 8 with valve 18, and line 20, which can be
combined to line 9 with valve 18. Line 19 is connected to line 20
through an adjustable pressure relief valve 22 and line 20 is
connected to line 19 through an adjustable pressure relief valve
21. Valves 21, 22 are, for example, spring-loaded valves, which are
attached, for example, mechanically. They determine the highest
pressure level of control circuit 15 and 27 when valve 18 is in the
right position. The pressure level varies depending on the rotation
difference and it is lower than the maximum pressure determined by
valves 10, 11.
In a mechanical solution stop 25, 26 controls, for example, stem
23, 24, which moves the set spring of valve 21, 22, which
determines the pressure level, wherein the valve opens and which at
the same time is the maximum pressure level of line 19 (together
with line 8) or line 20 (together with line 9). The pressure level,
together with the piston cross-section of cylinder 6 or 7,
determines force Fa or Fb, with which cylinder 6, 7 affects between
frames 4, 5, and therefore the supporting forces are affected at
the same time. Valves 21, 22 and cylinders 6, 7 are arranged in
such manner that when the rotation difference of frames 4, 5
increases, the pressure level also increases and at the same time
supporting force Fa, Fb increases. The direction of influence of
supporting force Fa when the direction of rotation is A is marked
in FIG. 1, and the direction of influence of supporting force Fb,
when the direction of rotation is B. A follower device, for example
stem 23, 24 can comprise, for example, a roll, which rolls along
profile 25, 26. The form of profile 25, 26 either pushes or pulls
the stem or the leverages controlling it, depending on the
implementation and where the valves 21, 22 and other parts of the
system are placed. For example, valve 21, 22 is attached to rear
frame 4 or to inner rim 2 and the wedge, pusher, buffer, or
leverage 23 to 26 is attached to front frame 5 or outer rim 3.
FIG. 2 describes the second advantageous embodiment of the
auxiliary control circuit 27, wherein pressure relief valve 21 is
the pilot valve of valve 10, which controls valve 10 to the desired
lower pressure level, which is the pressure level controlling the
aforementioned supporting force on line 9. Correspondingly valve 22
is the pilot valve of valve 11, which determines the pressure level
of line 10. Thus the pilot operation line 28 is connected to the
control connection in valve 10 and pilot operation line 29 is in
connection with the control connection in valve 11. Pressure relief
valves 21, 22 combine said lines 28, 29 with return line 17, which
feeding valve 14 also uses. Each pilot operation line 28, 29
includes, for example, a electrically controlled, normally closed
closing valve 30 and 31, which the control system controls
similarly to valve 18 in FIG. 1, but without free rotation, and
which is opened when the supporting forces controlled by valves 21,
22 are to be turned on. Closing valves 30, 31 can be replaced, for
example, by one two-position four-way directional valve, when the
free rotation is not taken into use, which is unnecessary when
using the supporting forces according to the invention.
In FIG. 1 the different directions of rotation of outer rim 3 are
marked with directions A and B. Correspondingly, the corresponding
directions are marked with profiles 24, 25. The mutual position of
profiles 24, 25 is, in addition, solid, and therefore in FIG. 1
only one profile controls a valve at a time, when the profiles in
reference position N do not control the valve. The so-called dead
zone around the reference position created with control is managed
in such manner that that the mutual position of profiles 24, 25 is
changed, in which case the extent of its rotation, during which
there is no control, can be managed. By positioning the profiles in
such manner that they control the valves simultaneously, there is
continuously some control pressure in the circuit. The
above-described effects are generated also by placement of limit
switches, or by electric control and sensor system, which creates
several different control possibilities. The position of profiles
in relation to the reference position can be different, in which
case when rotating to one direction A, the effect of supporting
forces begins earlier than when rotating to the other direction B.
Preferably the effect of the supporting forces is symmetric and
begins with the same value of rotation A and B. Control circuits 15
and 27 function in such a way, that when the direction of rotation
changes, the effect of valve 21 or 22 stops, and thus the
supporting force disappears as well, because the direction of
movement of cylinders 6, 7 changes. The movement of cylinders 6, 7
forces the medium to another valve 21 or 22, whose control
typically has only little effect after the reference position is
returned to and the rotation continues even over it.
FIG. 3 describes the effect of controls by means of a graph. The
horizontal axis shows the difference of rotation of frames 4, 5 as
degrees (deg), which in addition depends on direction A and B of
movement. The vertical axis shows supporting force F (N, Newton),
which is Fa or Fb affecting in frame joint 1. The disclosed control
is, according to FIG. 1, preferably progressive, i.e. continuously
rising when the difference of rotation increases. The form of
control is managed, for example, by forming profiles 25, 26 or,
more diversely, in control system 32. When using limit switches,
control is step-like and the number of steps varies, but is then
preferably rising as well. Graph 33 describes deviation from
reference position (0 deg) to direction A, in which case the
supporting forces, i.e. the forces Fa resisting the rotation
(caused by pressure of line 9) affect in the second chamber of
cylinder 6 in FIG. 1 and in the first chamber of cylinder 7, which
tend to decrease. Graphs 34 and 35 describe the change of direction
to direction B, in which case the first chamber of cylinder 6 and
the second chamber of cylinder 7 tend to decrease, which is now
resisted by pressure of line 8 (supporting force Fb), but only
after the reference position on graph 36, when the control of
profile 26 has an effect. This means that the return of frames 4, 5
to the normal position N according to FIG. 1 is not prevented and
the supporting forces do not have an effect then. There is a
corresponding function when returning from direction B. At the
intersection of graphs 33, 34 the rotation movement of frames 4, 5
can also be at rest for a while and the supporting force is
continuously on, because the supporting force of the control
circuit is thus adequate to cancel external force effects, which
tend to rotate the frames. Thus it must be noticed, that external
forces maintain pressure in that chamber of cylinder 6, 7 which
tends to decrease, in which case the same valve 21 or 22 takes care
of controlling the pressure of the medium. Therefore in this
situation external forces affect in a way that the difference
between rotations tends to increase even if the situation is
static, and frame structures 4, 5 still tend to rotate away from
normal position.
Movement to graph 34 and 35 takes place for example, after an
obstacle is crossed and frame structures tend to return to normal
position. At the same time the situation can be such that other
forces, such as the supporting forces affecting the wheel, even
help the return or they are reversed simply for the reason that the
mass center of the vehicle has moved and it causes a stabilizing
force or a force affecting in the opposite direction. At the same
time, in cylinder 6, 7 a different chamber tends to decrease, but
the supporting forces are not transmitted before the normal
position is regained or even surpassed.
The invention is not limited solely to the above-presented
embodiments, but it can be modified within the scope of the
appended claims.
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